Conformational analysis of saturated heterocycles. Part 91. Synthesis and conformational equilibria of 1-oxa-2,5-diazacyclohexanes

Abstract

Three examples of the novel 1-oxa-2,5-diazacyclohexane ring system were synthesised. Each shows two conformational barriers: (i) of 13.5–14.00 kcal mol^–1 corresponding to the slowing of ring reversal or N(2)–CH₃ inversion and (ii) of 7.5–8.2 kcal mol^–1 corresponding to slowing N(5)–CH₃ inversion. The proton and ¹³C n.m.r. spectra, and conformational equilibria of these compounds are discussed and compared with those for analogous saturated six-membered rings containing two heteroatoms.